The invention is directed to a starting device having an engaging relay whose armature axially displaces a pinion for the drive of a toothed rim of an internal combustion engine via an engaging lever, which pinion cooperates with a freewheel device and a starting motor, and having a locking apparatus which prevents the pre-engagement of the pinion when the engaging relay is not excited.
In automotive technology, such starting devices are used for starting the internal combustion engines of vehicles. In meshing systems provided with engaging relays, a pre-engagement drive is provided which engages a pinion of the starting device in a toothed rim of the internal combustion engine. When initiating the starting process, the engaging relay attracts and moves the pinion in the axial direction via an engaging lever in such a way that it can engage with the toothed rim of the internal combustion engine. A starter motor begins to rotate simultaneously. As soon as the pinion meshes in the toothed rim as a result of the thrust movement, it is securely held by it and moves further in the axial direction up to a stop as a result of the rotation of the starter motor with the aid of a steep thread associated with the output drive shaft. At the conclusion of the starting process, a return spring presses the armature of the engaging relay back and accordingly--via the engaging lever--presses the pinion back into its rest position. This disengagement is reinforced by the steep thread in the overrunning effected by the starting of the internal combustion engine. The freewheel device protects the starter rotor from excessive rates of rotation during the overrunning by the internal combustion engine. When the starter slows down due to braking moments, e.g. caused by a shaft sealing ring and/or the existing bearings, the output drive shaft which carries the pinion and is provided with the steep thread tends to move in the direction of the toothed rim of the internal combustion engine when the forces of the return spring acting against this movement are greater than the axial force component at the steep thread, particularly in free-thrusting starting devices. The pinion can accordingly run against the running toothed rim of the internal combustion engine and be damaged. To prevent this, known starting devices are provided with a ball lock for example. In the rest position, a spring-loaded slide secures the axial position of the output drive shaft carrying the pinion. In the unlocking process the aforementioned slide is displaced so that the ball can be displaced radially outward. This releases the output drive shaft for an axial movement. This ball lock requires high-precision structural component parts which are expensive to build, resulting in a complicated and expensive type of construction.